Jackdaws (Corvus monedula) were originally known as 'choughs',
a name derived from the bird's principal call. Jackdaws also utter
chattering calls, which sound like the word 'Jack' and so this name
also caught on. 'Daw,' or 'caw', is the typical call of the Rook.
'Crow' is a variant of 'caw'. From about the late 16th Century
onwards, 'Jack the daw' meaning 'the Jack-crow' began to replace
the older name 'chough'.

Another
crow, traditionally known as the 'Cornish Chough', has retained the
name 'Chough'. This species, which has a red bill and red legs, is
found on the sea-cliffs of the west of Ireland, Wales and
Scotland.

Jackdaws are endearing birds. The second smallest of our crows
(the Magpie is smaller), they are lively, tolerant of people and
swagger about in an amusing manner. However, they can block
chimneys with their nests.Captive Jackdaws are said to be good
mimics.

How
to identify Jackdaws:
Jackdaws associate with Rooks, but it is easy to tell the two
species apart. A Jackdaw is about one third smaller than a Rook and
is stockier. Both birds are black but the Jackdaw has a grey back
to its head and neck. The Jackdaw's conspicuous white eye gives him
a unique 'personality'.Adult Rooks, by contrast, have grey faces
but the head and neck are black. Rooks have dark eyes.

Where do they live?
Jackdaws are found throughout Ireland. They can occur in almost any
location. They like woodland and farmland but have adapted well to
cities and towns. You will also see them on the coast and on sea
cliffs. They particularly like fields with plenty of sheep and
cattle. The livestock keep the grass cropped short. This helps the
Jackdaws to find the beetles and insect larvae in the soil. Also,
the feet of livestock disturb the soil, exposing the larvae. Sheep
will tolerate Jackdaws on their backs. The birds pull out ticks and
take wool for their nests.

Jackdaws are great scavengers and frequent rubbish dumps. In
severe weather many move closer to human habitation.Jackdaw numbers
have increased in Ireland in the last hundred years. It is
estimated that we have about half a million of them at present.
Jackdaws, in this part of Europe, are sedentary but foreign birds
visit us in winter.

What
do they eat?
Jackdaws are general feeders. They eat insects, snails, slugs,
worms, frogs and mice, as well as vegetable matter, including
cereals, fruit and berries. Flies on cow-pats are a particular
favourite. Jackdaws will jump into the air to catch flying insects.
The birds will circle high in the air to catch swarming
ants.

Very
opportunistic, some Jackdaws seek unusual prey. They have been
recorded taking bats from a roost. Birds' eggs are occasionally
taken, sometimes those of Herons. Puffin and Guillemot eggs are
vulnerable at seabird colonies. Jackdaws can open milk bottles and
have been observed pulling up stringed peanut feeders to get at the
nuts. There is even a record of co-operative hunting, where a
Jackdaw provoked a Puffin into leaving its nesting burrow, enabling
the Jackdaw's mate to 'nip in' and steal the egg!

Jackdaws and Rooks tend to feed together. Rooks dig for their
food whereas Jackdaws go more for the surface insects and
snails.Like most crows, Jackdaws hide food, which they retrieve
later, but they do so to a much lesser extent than
Rooks.

Flocks:
Throughout most of the year Jackdaws live in small loose flocks
(seldom more than 40 birds). There is a loose hierarchy within a
flock. The highest rank goes to paired males who possess a
nest-site. Males are dominant to females. Older birds are higher in
the peck order than younger ones. In winter, Jackdaws and Rooks
congregate in trees to roost. These can number tens of thousands of
birds. In recent winters, there has been an impressive
concentration in the grounds of Malahide Castle.

Pairs
Pairs form in the birds' first year. There is a period of
familiarisation. The partners preen each other on their heads and
necks. Courtship feeding of the female by the male may take place
at any time of the year, but is particularly important to her
during the breeding season.

Most
Jackdaws pair for life and remain paired when in flocks. Divorces
tend to occur when the birds are young. The longer birds are
together the stronger the bond between them. Even after several
failed breeding attempts, a pair will usually remain together.
Divorce is expensive. A divorced bird loses its nesting site and
its rank in the flock. Bigamy, in which a male may have two females
on nests, occurs occasionally.

Territories
Jackdaws are loose colonial nesters, although some pairs nest on
their own. The pair defends a small territory in the immediate
vicinity of the nest.

Songs
Technically, Jackdaws are songbirds. We don't normally think of
their chattering and rasping as a song, but this is a prejudice on
our part. Jackdaws have a complex vocal communications system. Song
tends to be given when the male is alone and he may sing from a
perch or in flight. The chattering song is quiet and complex and
can last from several minutes. The functions and significance of
Jackdaw calls and songs are not well understood. Although recorded
in captive birds, mimicry is not known in the wild and nobody knows
why captive Jackdaws become mimics.

Mating
Copulation usually takes place at the nest, but it has been
recorded in flocks and at unusual times of the year. During the
laying stage, the male guards the female constantly. This helps to
ensure that no rival gets to fertilise the eggs and that the
rightful mate, who will have to work hard for several weeks, is
supporting his own young. Mating has been recorded during
incubation, the male mounting when the female was turning the
eggs.

Nests
Jackdaws may nest when they are a year old, but most pairs begin
nesting at the age of two.The nest is usually in a hole in a tree,
building or cliff. There may be a shortage of suitable holes.
Several pairs will use holes which are close together, forming a
breeding colony.

Both
partners build the nest and huge quantities of sticks can be
gathered. Very long sticks are collected at first. These form the
base of the nest. Progressively, smaller sticks are added as the
structure develops. The cup of the nest is lined with hair, grass
or fur. Jackdaws will perch on the backs of horses or sheep pulling
out hairs with which to line the nest. Occasionally, a pair builds
an open nest in a tree. The nest may even have a roof.

Eggs
Eggs are laid from the second half of April onwards. There are
usually between four and six, although there can be as many as
eight. Eggs are laid daily, but there may be a gap of two or even
three days. The female does the incubating and the eggs hatch after
about 17 days. She usually starts after the second or third egg,
but she may wait until the last one is laid. If she starts
incubating before all the eggs are laid, some eggs hatch earlier
than others.

Young
The young from the eggs which hatch first have a head start on the
later ones. They are bigger than their siblings and get most of the
food. With a plentiful supply of food all the young can survive,
but if food is scarce, the smaller late chicks will starve to
death. This is known as 'asynchronous hatching' and is a way of
ensuring that, with a variable food supply, nothing is wasted and
that as many chicks as possible are raised.

The
young are born blind, naked and helpless. Both parents feed them on
insect larvae. The babies can fly when about 30 to 35 days old.
They become independent of their parents about five weeks after
leaving the nest. Jackdaws produce only one brood each year.
Replacement clutches are unusual for Jackdaws.

Enemies
Jackdaw eggs are taken by rats and, very occasionally, by squirrels
or domestic cats. Other Jackdaws may steal eggs and young, although
they don't eat them. Large birds of prey such as the Peregrine or
the female Sparrow-hawk take both adult and newly-fledged Jackdaws.
Foxes will take newly-fledged young.

Mortality is high among young Jackdaws. On average, between one
and two young fledge per nest. Between 30% and 40% of fledged birds
die in their first year. Survival is only slightly better in
subsequent years. The oldest Jackdaw recorded in the wild was 14
years old.

Further information
An excellent summary of our knowledge of Jackdaws is given in the
Handbook of the Birds of Europe the Middle East and North Africa.
The Birds of the Western Palearctic. Volume IX. Editors Cramp &
Perrins. 1994.